For the characterization of technical surfaces and in particular for the derivation of roughness measurement values and also topographies, confocal microscopy is used nowadays as a standard method. The method is described for example in [M. Rohlres, J. Seewig, L “Optisches Messen technischer Oberflächen”, [“Optical Measurement of Technical Surfaces”] Beuth Verlag GmbH, Berlin, 2009]. In many confocal systems, scanning of the sample here takes place in all three spatial directions, that is to say that point scanning systems are firstly involved in which an optical beam is guided (scanned) over the sample in the x/y direction. In order to derive the height information, a movement of the sample relative to the detector unit (in the z direction) is furthermore required. From the intensity maximum depending on the z position, it is possible to derive the height information and thus the topography for each x y location. In this case, by way of example, the “Centre of Gravity” method is typically used [Tiziani et al., Opt. Eng. 39, 32 (2000)]. One example of such a system is the LSM700 from Carl Zeiss Microscopy GmbH.
What is disadvantageous about this method is primarily the long time required by the additional z scan for a 3D topography recording. Moreover, the precision (accuracy of the height measurement) is greatly dependent on the setting accuracy of the sample surface relative to the detector unit and is thus always limited, or a high precision requires highly accurate and expensive actuating elements e.g. on a piezo basis.